Besides the obvious, where else is a TII prone to have Vacuum Leaks?
 

I know my TII has an undiscovered Vacuum Leak somewhere and I'm determined to find it!!!! There is no leak on my intake or BOV. I checked all those hoses behind the intake manifold against the firewall, and they are fine too. There is also a bunch that go to my Solenoids that I haven't checked yet...where else can TII engines leak Vacuum?

A broken diaphram in the egr valve or the acv valve will constitute a vacuum leak. Suck on the hose going to the egr. If it won't hold a vacuum then the hose might as well be split open sucking air. Same with the acv, although there is only one line on that outfit that gets a vacuum. Its the nipple that strick straight up, should be the switching diaphram. Pull the hose off and suck. No vacuum equals a leak. Also a crudded up egr valve its self will cause a irratic idle. Never had that problem myself , but I understand you have to remove it and just clean the carbon off. Its on the right rear of the engine.Get a can of ether or starting fluid and spray at potential leaking areas and watch for changes in rpm.

*Check the 5/8" ID hose under the BAC valve - this is supposed to be clamped, but I have never seen one stock off the factory floor with clamps!
*Check the TID - it has a tendency to crack UNDERNEATH, so it's hidden from view.
*Fuel injector lower grommets get hard with heat and age - trouble-shoot as described below.

You can track down vacuum leaks by spraying CARB cleaner in and around the engine while it's idling.&nbsp Just shoot and area for 1-2 seconds and wait 10 seconds to see if the idle changes; if the idle changes, a vacuum leak is in that area.&nbsp Shoot along the intake tract.&nbsp Shooting under the intake manifold will uncover if your fuel injector grommets are leaking or if any of the vacuum hoses that connects the solenoids are.



-Ted

Well you said not obvious, but if you want obvious, take off the turbo inlet duct and examine it with your eyeball for a crack where the clamp is located in particular. Its a hard area to spray with Starter Fluid because of the underbelly pan and the fan blowing. It can be done from below but by the time you remove the underbelly pan you could have removed the duct.

Thanks for the ideas so far people...one thing I never checked out was my ACV system. I'm going to look into that...